What is the best network printer to buy when operating on multiple OS in one dept.

I work for a company who's IT department doesn't really support Macs so I am hoping I will find some ideas here.

I have 5 imacs on 10.6, a server running 10.5 and a mac book air running 10.7

We currently have a b/w printer HP laser jet 8150N that doesn't play well with all of the work stations. We have almost no error messages. Used to get broken pipe, broken null messages and how it does things like pauses in one print monitor, it won't print and drop out of the print monitor and other times it spits blank pages or characters. Really never having any errors on the local machine or the window of the printer.

Nothing is the same, different computes and different times. When one part of the department is having issues the others are not. I know I want to replace the machine, and I know I should get all computers on the same OS but here is my further issues.

My other printer (color that is leased) they do not want me to upgade to 10.7 as they say they are still having issues printing and don't have the correct drivers etc.

We are a Graphics department and I need something fast and reliable. We went from an IBM infoprint 1145 to an HP laserjet 8140N
I need 8.5 x 11 and 11x17 options and be able to duplex. Any suggestions on the OS issue and what printer might be best?

Our leased printer is an MPC 6000 but we are probably switching to a Sharp unit (not decided on model number) Ricoh gave us one driver for emails and one driver for other it works ok, the Sharp unit they saw stay away.

The main issue though is the fact that we have a primary b/w printer that we own and I need to figure out a solution that will work with both the sharp and the new b/w. Note there is more times than not they will purchase a used or referb on the b/w. The chance of a new unit is pretty much impossible.

We have deleted several times and set up a new printer profiles. Also we have made sure we had the newest drivers. The only other issue with this HP with it IP address as when you set it up it doesn't seem to see it over the network.

Slight update. Found another printer in the network and tested files that failed from two computers (2 OS). It was an IBM Infoprint 1352. It printed fine and without issues. Tried files that could print and even running down a flight of steps it still printed faster than to the HP. Don't know if any of this helps.

But, when we had a print shop, we had good luck with HPs, for B&W, up to 11x17, service was fair but good machines. We also had a high end digital copier, but that's probably not your goal here.

We sold the shop, but still do a lot of graphic work and have two Macs and a PC that use a Xerox 6280N for B&W and color, but only 8.5x11. However, the cost for the quality is outstanding. It is hooked directly to the airport via hub and the Macs work flawlessly wireless, the PC is wired to the hub, but probably could be wireless...just haven't tried it.

We also have had a brother, still have a B&W Brother that is an inexpensive 7360N, multifunction printer, that is also flawless, but a bit awkward for faxing.

The Xerox support is fair, and probably not much better than HP, and is costly. The Brother support (on several machines) is outstanding and no charge, but Brother does not have the quality for color, or I would have stayed with them.

I agree with the other guys - shouldn't be a problem for any network printer. I suspect you haven't told us all we need to know -
Are computers and printers in the same subnet?
Are you using Bonjour or IP printing to set up?
Are you comparing apples to apples? Using same driver (like, say, postscript) on every computer?